Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease with poorly understood etiology and pathogenesis and for which adequate treatment options are limited. Although dysregulated production of autoantibodies and immune complex deposition are considered hallmarks of SLE, considerable evidence supports the hypothesis that auto reactive lymphocytes are implicated in disease. SLE patients have several T cell defects including aberrant signaling, suboptimal IL-2 production, lower regulatory T cell frequencies, high CD4-/CD8- Th17 T cells, and sustained abnormally high intracellular calcium. Effector memory T cells (TEMs) decrease in circulation and increase in the kidneys and urine of lupus nephritis patients, suggesting that renal infiltration of this T ell subtype contributes to disease. Activation and inflammatory cytokine production by effector memory T cells requires expression of Kv1.3, a potassium channel needed for sustained intracellular calcium levels in effector memory T cells that have been found to be autoreactive and pathogenic in several autoimmune diseases. Here we propose to evaluate the levels of expression of Kv1.3 in SLE T cells in peripheral blood of inactive and active SLE patients compared to normal healthy controls, and test the functional effect of blocking the Kv1.3 channels in these cells with Kineta's drug candidate Kv1.3 specific peptide blocker ShK-186 (dalazatide) in terms of calcium flux and cytokine production ex vivo. In addition, we will evaluate Kv1.3 expression in kidney biopsies from patients with lupus nephritis and correlate expression to disease activity. This study will inform our hypothesis that Kv1.3 expressing T cells are pathogenic in SLE and may support considering evaluation of ShK- 186 in SLE patient populations in clinical trials.